NTN 6307 LU Kugellager (35x80x21)

The principal dimensions are 35x80x21 mm at a weight of 0.46 kg; the further technical details are listed in the specification table. This variant features a contact seal. A contact seal on one side separates two worlds: outside the loaded surroundings, inside the lubricant-supplied space of the assembly. This version applies the selectivity of a contact seal exactly where it is needed and leaves the opposite side open.

On the closed side an elastomeric lip bears against a shoulder or in a groove of the inner ring; it is this contact that turns a restriction into a barrier which also keeps out splash water, spray mist and fine dust — an effect a non-contacting shield does not achieve. On the open side the rolling chamber remains accessible, so lubricant from the surrounding space reaches the rolling contact, frictional heat can be carried away with it and relubrication through the assembly remains possible; the position is thereby not committed to an enclosed grease charge dimensioned for the service life.

The price of the contact arises on one side only: the load-independent frictional torque and the heat source it creates at the inner ring occur at one lip instead of two, so breakaway torque, no-load loss and permissible speed lie between the doubly sealed and the open version. The mounting instruction follows from the asymmetry: the seal faces the loaded surroundings, the open side the clean interior, and a reversed position inverts this assignment without being noticeable during assembly.

The lip is a wearing part whose barrier effect declines over operating time with circumferential speed, temperature and medium. Normal radial clearance is matched to one interference-fitted ring and a moderate temperature gradient, whereby the frictional heat of the single lip is to be attributed to the inner ring. Through-hardened standard bearing steel sets the frame for the ratings listed in the catalogue; the temperature limit of the sealing material is to be taken from the designation.